Abstract: In order to clarify the impact of extreme precipitation and human activities on sediment transport in the Jinsha River Basin,  daily precipitation data from 1974 to 2018 at 27 meteorological stations in the basin and its surrounding areas were collected. Seven extreme precipitation indices were selected and calculated using RClimDex model. The spatiotemporal distribution characteristics of each extreme precipitation index were analyzed. The double accumulation curve method and random forest model were used to quantitatively calculate the contribution of extreme precipitation to the reduction of sediment transport. The conclusions were as follows: (1) All the extreme precipitation indices showed an upward trend except CWD. The duration of the heavy precipitation events gradually extended, and the precipitation intensity increased significantly. The southeast of the basin was the main area of heavy precipitation. The precipitation intensity gradually decreased from the southeast to the northwest, while the precipitation duration was the longest in the middle of the basin. (2) Abrupt changes occurred in the annual sediment transport in 2002 and 2013. The double accumulation curve method showed that CWD, the number of consecutive rainy days, had the greatest impact on the reduction of sediment transport during 2003-2013, with a rate of 3.8%. The heavy precipitation index (R95P), had the greatest contribution rate during 2014-2018, with a rate of 4.1%; The random forest model revealed that the influence of extreme precipitation index on sediment transport reduction was less than 10%. (3) The effects of human activities on sediment transport were further analyzed through the changes of land use types in the basin and sediment containment of nearby reservoirs during 1980-2018. Since the 21st century, human activities in the basin had become more intense, and a large amount of unused land had been transformed into grassland. The sediment retention rate of large hydropower stations in Shigu - Pingshan Station during 1974-2013 was calculated, and the sediment retention rate was all above 60%, i.e., the sediment retention effect of the reservoir was obvious.  In summary, human activities were the main factors leading to the decrease of sediment transport in the basin. The extreme precipitation had little influence on the change of sediment transport in the basin. The contribution of different precipitation indexes was different from each other.